Re: Signalling queries

["B." <b.spammed@four12.net>]

"Bradley Torr" <truenorth@one.net.au.SPAMTRAP> wrote in message
01c0f251$6cfd8280$c73e0c3d@default">news:01c0f251$6cfd8280$c73e0c3d@default...

> Hello all,

> Being only an interested layman when it comes to railway technology -
> my railfan interests mainly centre upon the generalities and the
> political, geographic and social aspects of railway systems - I don't
> know much about signalling, but I'd like to know more about it. To this
> end, I have several questions regarding signalling theory and practice.

> * What is the difference between 'train order working' and 'staff
> working'?  I believe that staff working is centred around the idea of
> 'staffs', which I have heard being referred to as pegs or tokens, which
> are carried by train crews and then placed into a machine at certain
> points along a line in order to access the next section of the line..
> am I correct?

Train Staff & Ticket (Vic) or Ordinary Train Staff?? (NSW):

There is one Staff for each section.  At each end of the section there is a
Ticket Box, which is unlocked by the Staff.  In the Ticket Box is kept a
book of *tickets* (as if you couldn't see that coming).  If there is a train
to go thru the section, and the next train after that is going to be coming
in the opposite direction then the 1st train will take the staff.  If the
2nd train is to *follow* the 1st train, then the 1st train will run on a
ticket, the driver in this case is supposed to sight the staff to prove that
it is at this end of the section.  One the first train has arrived at the
far end, a special message (the ACRE) is sent back to the first station, and
the 2nd train can then enter the seciton on the staff.

Electric Staff:


This is much easier.  There is an instrument at each end of the section,
these are electrically interlocked with each other.  There are many staffs
for each section which are kept in the instrument, but the electric
interlocking means only 1 staff can be withdrawn out of the instruments at a
time.  So the 1st train takes a staff, when it gets to the other end the
staff is returned to the instrument at that end.  The next train can come
along, from either direction, and all that needs to be done is withdraw a
staff.

Train Order:

This is where the authority to enter a section is by means of a written
'Train Order' which is transcribed over the radio/phone from the Train
Controller at a central location.  When the train gets to the other end of
the section, the train can 'fulfil' or 'relinquish' the train order,
basically the driver contacts control and says 'I have arrived complete at
Gunzelville Loop....".  The big benifit of Train Order working is that you
can get one order to cover many sections, and thus you dont have to stop at
each intermediate station to change staffs.  Plus you don't need much at all
in terms of lineside infrastructure, e.g. no pole line, quite possibly no
signals etc...  The disadvantage is that there is a lot of reliance on
humans not making a big cock up, which they did quite spectacularly at Mt
Christie for example.

> * What does "CTC" stand for, and what does it mean?

Centralised Traffic Control.  It's where you have all the signalling for a
particular section of line, usually a long section, controlled from the one
place.  E.g. Junee to Albury is worked by CTC, it's all controlled from
Junee.  The trains just obey the signal aspects, and there are no Train
Orders or Staffs involved.

> * When a train enters a signalling section, the first set of wheels on
> a train make contact with track circuits, which alert the signalling
> system that the train is entering a new section. How does a signalling
> system know that the train has left the previous section, though?

Basically with a plain track circuit the track is broken up into sections
with insulated joints.  At one end of the track a voltage is fed into the
track, and at the other end there is a relay.  When the train comes along,
it short cirucits the 2 rails together, this short circuits the relay, and
it drops out.  When the train leaves the section, the short circuit
disappears, and the relay can pick up again, indicating that the train is
out of this particular section.

> * I remember, during a journey in an Endeavour from Moss Vale to
> Macarthur in February 2000, seeing a sign somewhere around Picton on
> the Down saying something like "BEGIN SINGLE LIGHT INDICATION". I also
> notice that most signalling here in Wollongong is single light. At
> which points radiating from Sydney does double light signalling end and
> single light signalling begin?

Dunno.  Ask me a Victorian question... |-)

> Thanks in advance for your kind and intelligent and constructive
> answers.

In the sandpit?  You'll be lucky...

--
B.

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